As is known, handheld digital audio systems are becoming very popular. Such systems include digital audio players/recorders that record and subsequently playback MP3 files, WMA files, etc. Such digital audio players/recorders may also be used as digital dictaphones and file transfer devices. Further expansion of digital audio players/recorders includes providing a radio receiver such that the device offers frequency modulation (FM) or amplitude modulation (AM) radio reception.
While digital audio players/recorders are increasing their feature sets, the increase in feature sets has been done in a less than optimal manner. For instance, with the inclusion of an FM receiver in a digital audio player/recorder, the FM receiver is a separate integrated circuit (IC) from the digital audio player/recorder chip set, or IC. As such, the FM receiver IC functions completely independently of the digital audio player/recorder IC, even though both ICs include common functionality.
Four papers teach FM receivers that address at least one of the above mentioned issues. The four papers include, “A 10.7-MHz IF-to-Baseband Sigma-Delta A/D Conversion System for AM/FM Radio Receivers” by Eric Van Der Zwan, et. al. IEEE Journal of Solid State Circuits, VOL. 35, No. 12, Dec. 2000; “A fully Integrated High-Performance FM Stereo Decoder” by Gregory J. Manlove et. al, IEEE Journal of Solid State Circuits, VOL. 27, No. 3, March 1992; “A 5-MHz IF Digital FM Demodulator”, by Jaejin Park et. al, IEEE Journal of Solid State Circuits, VOL. 34, No. 1, Jan. 1999; and “A Discrete-Time Bluetooth Receiver in a 0.13 μm Digital CMOS Process”, by K. Muhammad et. al, ISSCC2004/Session 15/Wireless Consumer ICs/15.1, 2004 IEEE International Solid-State Circuit Conference.
While the prior art has provided FM decoders, a need still exists for a method and apparatus of radio decoding that is optimized to function with a digital audio player/recorder to produce an optimized handheld audio system.